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Set the greeting for a chat UI

Source: R/chat.R
chat_set_greeting.Rd

Sets or clears the greeting displayed in an existing chat_ui(). The greeting is shown when the chat first loads and is dismissed when the user sends their first message.

Call chat_set_greeting() from the server to display a dynamic or streaming greeting. This is typically used inside an shiny::observeEvent() watching input$<id>_greeting_requested – an event that fires when the chat is visible, has no messages, and has no greeting set. See the Greeting section in chat_ui() for details on greeting_requested.

If the greeting has already been dismissed, calling this function updates the greeting content but does not make it visible again. To show a new greeting after dismissal, first clear the chat with chat_clear(id, greeting = TRUE).

Pass NULL to clear the current greeting entirely.

Usage

chat_set_greeting(id, greeting, session = getDefaultReactiveDomain())

Arguments

id

The ID of the chat element

greeting

The greeting to display. Can be:

session

The Shiny session object

Value

Returns invisible(NULL) for static and NULL greetings, or a promise for streaming greetings (resolves when streaming is complete).

Examples

if (FALSE) { # interactive()
library(shiny)
library(bslib)
library(shinychat)

# Static greeting set from the server
ui <- page_fillable(chat_ui("chat"))

server <- function(input, output, session) {
  chat_set_greeting("chat", "## Welcome!\n\nHow can I help you today?")

  observeEvent(input$chat_user_input, {
    chat_append("chat", paste0("You said: ", input$chat_user_input))
  })
}

shinyApp(ui, server)
}
if (FALSE) { # interactive()
library(shiny)
library(bslib)
library(shinychat)
library(coro)

# Streaming greeting generated by a function
greeting_generator <- async_generator(function() {
  for (chunk in strsplit("## Hello!\n\nHow can I help you?", "")[[1]]) {
    yield(chunk)
    await(async_sleep(0.02))
  }
})

ui <- page_fillable(chat_ui("chat"))

server <- function(input, output, session) {
  chat_set_greeting("chat", chat_greeting(greeting_generator()))

  observeEvent(input$chat_user_input, {
    chat_append("chat", paste0("You said: ", input$chat_user_input))
  })
}

shinyApp(ui, server)
}
if (FALSE) { # interactive()
library(shiny)
library(bslib)
library(shinychat)

# LLM-generated greeting using greeting_requested
ui <- page_fillable(chat_ui("chat"))

server <- function(input, output, session) {
  chat_client <- ellmer::chat_openai(model = "gpt-4o")

  observeEvent(input$chat_greeting_requested, {
    stream <- chat_client$stream_async(
      "Generate a short, friendly welcome message."
    )
    chat_set_greeting("chat", chat_greeting(stream))
  })

  observeEvent(input$chat_user_input, {
    stream <- chat_client$stream_async(input$chat_user_input)
    chat_append("chat", stream)
  })
}

shinyApp(ui, server)
}
if (FALSE) { # interactive()
library(shiny)
library(bslib)
library(shinychat)

# Regenerate pattern: chat_clear(greeting = TRUE) triggers greeting_requested
ui <- page_fillable(
  chat_ui("chat"),
  actionButton("regenerate", "New greeting")
)

server <- function(input, output, session) {
  observeEvent(input$chat_greeting_requested, {
    chat_set_greeting(
      "chat",
      paste("## Welcome!\n\nGenerated at", Sys.time())
    )
  })

  observeEvent(input$regenerate, {
    chat_clear("chat", greeting = TRUE)
  })

  observeEvent(input$chat_user_input, {
    chat_append("chat", paste0("You said: ", input$chat_user_input))
  })
}

shinyApp(ui, server)
}